Princess Charlotte sticks out her tongue at Buckingham Palace for RAF 100

Just a day after the 3-year-old royal made headlines for her adorable (and frankly, polite) antics at her little brother Louis' christening, the tot has once again stolen the show -- but this time with a naughty moment.

The royal family, including Duchess Kate, Prince William, Duchess Meghan and Prince Harry, joined Queen Elizabeth on the balcony of Buckingham Palace on Tuesday morning to mark the Royal Air Force's 100th birthday. Passersby were treated with a special flypast, a show that included Prince George and Princess Charlotte as spectators from inside the palace.

Charlotte, ever the handful, took the ceremony as an opportunity to entertain photographers, with a few signature waves. At one point, however, she decided to stick out her tongue to the crowds and bang on the window. It's a "naughty" move she's been spotted pulling a number of times, most recently at the royal wedding back in May.

See the hilarious moment unfold in the video above!

For more adorable Princess Charlotte moments, scroll through below!

PHOTOS: See the princess' funniest faces

Video: We Couldn't Get Enough of Princess Charlotte at Her Brother's Christening